Translatable support for moving the vacuum system and the mass spectrom-eter relative to the magnet



Sept. 10, 1968 R. A. ERICKSON 3,401,405

TRANSLATABLE SUPPORT FOR MOVING THE VACUUM SYSTEM AND THE MASS SPECTROMETER RELATIVE TO THE MAGNET Filed April 4, 1966 I NVE NTOR.

RAYM ND A ERlCKSON ORNEY United States Patent '0 3,401,405 TRANSLATABLE SUPPORT FOR MOVING THE VACUUM SYSTEM AND THE MASS SPECTROM- ETER RELATIVE TO THE MAGNET Raymond A. Erickson, San Jose, Calif assignor to Varian Associates, Palo Alto, Calif., a corporation of California Filed Apr. 4, 1966, Ser. No. 539,918 2 Claims. (Cl. 250-413) ABSTRACT OF THE DISCLOSURE A mass spectrometer system is disclosed. The mass spectrometer includes an ion mass analyzer chamber disposed in the magnetic gap of a magnet. The magnet includes a yoke structure interconnecting the poles of the magnet and bridging across the magnetic gap externally of the gap. A vacuum system, including a pair of vacuum pumps and a rigid exhaust manifold, is connected to the mass analyzer chamber for evacuating the chamber. A hanger structure is affixed to the yoke of the magnet for supporting the mass analyzer and vacuum system. A movable carriage supports the vacuum system and mass analyzer from the hanger structure. The movable carriage includes a pair of parallel rods passable through and axially slidable through the hanger structure. A drive screw is aflixed to the carriage and the drive screw threadably mates with a threaded portion of the hanger over only a limited extent of the full movable travel of the support rods through the hanger. The support rods have a sufiicient length such that the full extent of movable travel of the carriage is sufiicient to move the mass analyzer chamber substantially out of the gap of the magnet to facilitate access to the mass analyzer for maintenance and the like. Adjusting screws are provided on the hanger structure for producing small adjustments of the position of the mass analyzer within the gap of the magnet.

In a high resolution cycloidal mass spectrometer, a relatively large magnet is needed to provide a relatively large volume of uniform intense magnetic field over the mass analyzer region of the apparatus which is evacuated to a low pressure as of torr. It is desirable that the mass analyzer portion of the apparatus be translatable within the field of the magnet in order to position the mass analyzer within the most uniform portion of the magnetic field. Although flexible corrugated metallic vacuum plumbing could be employed to permit fixed mounting of the vacuum pumps with translation of the mass analyzer such plumbing is expensive and serves as a source of system contamination due to its large internal surface area.

In the present invention, the vacuum system including the pumps, exhaust manifold and mass analyzer are mounted on a movable carriage supported from the yoke of the magnet, whereby the mass analyzer may be adjustable positioned, as desired, within the field of the magnet while permitting use of rigid vacuum plumbing fittings. In a preferred embodiment of the present invention, the movable carriage is hung from the magnet yoke and includes means for adjusting the axial position of the mass analyzer in the gap as well as adjusting the mass analyzer in the horizontal and vertical directions in the transverse plane of the gap.

The principal object of the present invention is the provision of an improved cycloidal mass spectrometer.

One feature of the present invention is the provision of a movable carriage having a pair of parallel support rods with the mass analyzer and vacuum system of a mass spectrometer mounted thereto and being adjustably translatable within the gap of a magnet for adjustably ice positioning the mass analyzer within the field of the magnet, whereby optimum operating magnetic field conditions for the mass spectrometer are obtainable.

Another feature of the present invention is the same as the preceding wherein the carriage is independently movable in two orthogonal directions within a plane at right angles to the direction of the magnetic field of the magnet.

Another feature of the present invention is the same as any one or more of the preceding wherein the carriage, with dependent mass analyzer, is axially translatable in the direction of the magnetic field of the magnet.

Another feature of the present invention is the same as any one or more of the preceding features wherein the carriage is suspended from the yoke of the magnet.

Other features and advantages will become apparent upon a perusal of the following specification taken in connection with the accompanying drawings wherein:

FIG. 1 is a side elevational view, partly in section, of a cycloidal mass spectrometer employing features of the present invention,

FIG. 2 is a fragmentary View of the structure of FIG. 1 taken along line 2-2 in the direction of the arrows, and

FIG. 3 is a view of the structure of FIG. 1 taken along line 3-3 in the direction of the arrows and partially broken away.

Referring now to the drawings, a cycloidal mass spectrometer 1 is disposed in the gap 2 of a powerful electromagnet 3. The magnet 3 provides an intense variable magnitude magnetic field H as of 1000 G to 10,000 G over the mass analyzer portion 4 of the spectrometer. The analyzer portion 4 is contained within a thin rectangular vacuum envelope section 5 as of Ms" thick sheet stainless steel. The analyzer portion 4 is supported within the envelope 5 from a thick walled rectangular demountable flange assembly 6.

Gas to be analyzed is introduced into the analyzer portion 4 through a gas inlet manifold 7 passing through the demountable flange assembly 6. Within the analyzer portion 4 the gas to be analyzed is ionized and projected through a narrow slit into an array of rectangular electric field producing electrodes which produce a uniform ion accelerating electric field at right angles to the magnetic field H. Under the influence of the crossed electric and magnetic fields, the ions are caused to execute cycloidal trajectories. Those ions of a common mass-to-charge ratio are focused through a detector slit and detected to give an output in accordance with their mass-to-charge ratio. The magnetic field intensity H is scanned to successively focus ions of different mass-to-charge ratio through the detector slit to yield an output mass spectrum of the gas under analysis. The spectrum is recorded on a recorder, not shown.

The envelope 5 containing the mass analyzer section 4 is evacuated to a low operating pressing as of 10- torr via a pumping system 8 connected to the envelope 5 via a rigid metallic exhaust manifold 9 as of welded 1.5" diameter stainless steel pipe. The pumping system includes a refrigerated sorption pump 11 and a getter ion vacuum pump 12. The exhaust manifold9 includes various pipes 13 and valves 14 as of stainless steel interconnecting the vacuum envelope 5 and the pumps 11 and 12. The exhaust manifold 9 also includes a stainlesssteel pipe 13 interconnecting the gas inlet system 7 and the pumps 11 and 12 for drawing a vacuum for the two stage direct sample introduction lock of the gas inlet system 7.

A movable carriage assembly 15, having the vacuum system of the mass spectrometer depending therefrom, is hung from the yoke of the magnet 3 such that the mass analyzer portion 4 of the spectrometer 1 may be adjustably positioned in the magnetic field for optimum per- .formance of the spectrometer 1. The-carriage includes a pair of'horizontally directed' parallei support rods 16 and 17 as of 1" diameter precision ground case hardened carbon steel approximately 21" in' length. The carriage support rods 16 and 17 are fixedly secured, at one end, to a right angle bracket 18 as of 1' thick aluminum plate which in turn supports the vacuum purnps 11' and 12 and exhaust manifold 9 therefrom. The carriage support rods are fixedly secured at their other ends to a second right angle bracket 19 as of 1 thick aluminum plate which is bolted to the fixed flange-ofthe demountable flange assembly 6 of thevacuum envelope 5. The bracket 19 is relieved at its corner 21 to facilitate access to the demountable flange portion of 'the flange assembly 6.

One carriage support rod 16 slides through a pair of bronze bushings 22 mounted in the leg portions 23 of an inverted U-shaped hanger member 24"hung over the soft iron yoke 25 of the electr0rnagnet3. The other carriage support rod 17 passes through a. notched out portion 26 (see FIG. 3) of the legs 23 of the hanger 24 and is vertically supported from the hanger 24 via a pair of roller bearings 27 carried from the legs 23 of the hanger 24. The combined bushing and roller bearing support for the carriage rods 16 and 17 readilypermits horizontal rectilinear translation of the carriage 15 in the X direction without bending of the rods 16 and 17.

A drive screw 28, for the carriage 15, is captured in the bracket 19 via retaining rings, not shown, and is provided at its outer end with a hand crank 29 for turning.

The drive screw 28 is of limited length as of 3" and threadly mates with a threaded bore 31 in one of the legs 23 of the hanger member 24. Rotation of the drive screw 28, by turning of the hand crank 29, causes the carriage 15 to move over a limited distance as of 1.5 in the X direction. When the drive screw 28 has been screwed out of the bore 31, the carriage is freely slidable in the X direction and as a result the carriage may be pulled to its furthermost +X extent of travel to facilitate access to the demountable flange assembly 6. An adjustable screw 32 is threaded into the bracket 19 and bears against the leg 23 serving as an-adjustable limit stop for the X direction of travelfpr the carriage 15. p

The hanger member 24 is positionedvertically over the gap 2 on the yoke portion passing vertically over and extending horizontally across the gap 2 in the Z direction,

tion 4 permits adjustment of the axial position of the analyzer in the gap 2 of the magnet 3, i.e., along the Z axis, such that the ion bea'minside the: analyzer may be positioned in the most uniformmagnetic field region, typically in the center transverse plane of the gap 2. The jack screws also permit vertical translation of the ion beam, i.e., along the Y axis, to position the ion beam in the most uniform magnetic field region of the gap. The drive screw 28 permits adjustment of the position of ion beam in the X direction to a region of most uniform magnetic field. In practice, the jack screws 35 and drive screw 28 are separately adjusted for optimum resolution of the output mass spectra. Then screw 34 is tightened down to hold the hanger 24 in that preferred position. Then the X axis stop screw 32 is set'for this position. Once these adjustments have been made, the carriage 15 may be pulled out for maintenance and returned to its original position by merely advancing the drive screw 28 until the stop 32 is engaged.

Since many changes could be made in the above construction and many apparently widely difierent embodi ments of the invention could be made 'Witl'lOlJt departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a mass spectrometer apparatus, means forming a magnet defining a magnetic gap, means forming an ion mass analyzer disposed in the magnetic gap for separating ions and giving an output according to the respective mass-to-charge ratio, means forming a vacuum system for evacuating said mass analyzer, means forming a movablecarriage having said mass analyzer meansand said vacuum system means dependent therefrom and movable therewith for adjustably positioning said mass analyzer means within the magnetic gap of said magnetmeans, a yoke member extending across the magnetic gap, a hanger member aflixed to said yoke portion of said magnet for suspending said carriage means from said yoke portion, said movable carriage means including a pair of elongated parallel support rods axially slidable through said hanger structure, means forming a drive screw aflixed to said carriage, said drive screw threadably mating with a threaded portion of said hanger structure over only a limited extent of the full movable travel of said support rods through said hanger, said parallel support rods having a sufiicient length suchthat the full'extent of movable travel of said carriage is suflicient to move said mass analyzer means substantially out of the gap of said magnet to facilitate access thereto for maintenance.

2. The apparatus according to claim 1 wherein said vacuum system means is rigidlyinterconnected to and fixed in position relative to said mass analyzer means, and including means for adjusting the position of said mass analyzer means separately along two orthogonal direc- 'tions in a plane transverse to the direction of the magnetic field in the gap of the magnet means.

References Cited UNITED STATES PATENTS 2,544,717 3/1951 Nier 250-419 WILLIAM F. LINDQUIST, Primary Examiner. 

